A helicopter flight control device makes it possible to control movement of the helicopter via movements imposed by the pilot on a control lever. By way of example, the collective pitch of a helicopter makes it possible to change the inclination of the blades in order to cause the helicopter to rise or descend.
However, when the pilot varies the collective pitch, that action modifies the power delivered by the main turbine. Thus, the pilot must continually ensure that the speed limits of the turbine (running too fast or too slow) are not reached when varying the collective pitch even though those limits can themselves change, for example as a function of stages of flight (takeoff, climbing, descending . . . ). That greatly complicates a pilot's workload.
In order to assist the pilot, it is known to warn the pilot by using an audible or visual alarm when the helicopter is approaching or has reached the speed limits of the turbine (running too fast or too slow) while the collective pitch is being varied.
That type of warning may however be bothersome and stressful for the pilot in the long term.